This is going to be a really short review and i apologize for that.

Story (7): The story was interesting, it was original in its ways but nothing to make you jump of your seats.
Regular... Interesting as a manga, but nothing else...

Art (6): The Art is not bad, the characters are well done, but as a monthly manga... it seems really pathetic (the backgrounds or characters dont have a really good quality...)
Full Metal Alchemist, Claymore, And lots of other monthly mangas have a WAY better Art...
(I dont want to make it extensive but if you read monthly mangas you would see that even the ones that dont need a great art are still better in this aspect.)

Characters (6): Hifumi is interesting but most of the characters lacks charm, and the art dont help them at all.

In Overall i have to say that Change 123 is not a bad manga, but as a monthly it dissapointed me.
This manga did enough to be worth reading but nothing else, dont expect this to be your favorite manga...